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Case Histories: 38 Super Auto +P

Case Histories: 38 Super Auto +P

The father of this month’s subject has just celebrated his 115th birthday. His son was a bit of a child prodigy but for us in the UK, was forced into early retirement. Dad is better known as the Colt .38 Auto, aka .38 ACP, (NOT to be confused with the .380 ACP). It was originally introduced in 1900 in the Colt 38 Automatic Pistol. His lad is the .38 Super Auto (later +P). It was a semi-rimmed straight wall case with at 0.900”, originally containing a 130-grain pill. Indeed, the difference is only in their performance, hence the need for an unmistakable change to the headstamp. Original loadings in the .38 ACP had proved too hot for the Colt .38 Auto pistol and were down-rated. The development of the much stronger Colt 1911 paved the way for a return to the original ballistics and in 1926 the .38 Super Auto was ‘reborn’. In order to avoid confusion most commercial .38 Super Auto ammo was produced with nickled cases.

SAVED BY A CHANGE IN HEADSPACE

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A straight wall semi-rimmed cartridge head spacing on a vestigial rim in a semi-auto pistol was not a recipe for optimum performance. It soon gained a reputation for case damage and modest accuracy; as a consequence the only pistol chambered for it was the Colt 1911. It was Irv Stone, an independent barrel maker and founder of Bar-Sto Machine who, in the late 1960’s resolved the issue by designing a drop-in barrel for the 1911 which head spaced on the case mouth. Suddenly the picture changed. Many early practical style pistol shooters using cheap and plentiful ex-Govt. Colt 1911 pistols in .45 ACP seized the advantage.

The new accuracy, reliability and increased capacity that the drop-in .38 Super Auto barrel offered was a game changer. Not that all was sweetness and light, with the semi-rim still causing feeding issues in some magazines. Nonetheless, custom shops and other makers such as Kimber and STI offering their versions of the 1911 soon added the calibre too. The proliferation of both arms and ammo in .38 Super Auto lead in 1974 to a SAAMI agreement with the industry to reinforce the identity of the cartridge with the addition of +P to all cases, packaging and arms. To aid feeding and extraction issue some brass makers now offer hybrid cases called the Supercomp, Super Lapua, Super RL (and others) with the diameter of the semi-rim reduced to around .006” over body diameter. These are generally offered ‘in the yellow.

POWER TO PERFORM

The default performance of the Colt .38 Auto cartridge with the .356”, 130-grain JRN was around 1000 fps, the .38 Super Auto delivers some 1350 fps, far too hot for the original Colt .38 Auto pistol. As the popularity of the calibre increased, especially in those countries that embraced IPSC, more makers offered it. The 130-grain FMJ is still the default with 100, 115, 125 and 147-grain HP and SP variants also available. Most, but not all makers still follow the nickled case convention. Unlike 9mm, the stock .38 Super Auto +P will make Major Power Factor (bullet weight x fps divided by 1000) in IPSC without the need for dangerous overloads, a situation further eased by the Power Factor reduction from 175 to 165 a few years ago. Whilst I’ve not examined every brand of the cartridge, most makers now employ .355” bullets, in common with those used in 9mm ammo. I’ve yet to encounter a rifle chambered for this calibre so we’re down to Section 7/3 collectibles.

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